The attitude and heading of a vehicle can be essential information which is typically provided by systems using inertial sensors. Using a Global Navigation Satellite System (GNSS) for attitude sensing offers a lower cost, lower weight, smaller volume, and lower power consumption alternative. GNSS attitude determination works by differencing the carrier-phase signals of multiple receivers/antenna pairs. While carrier phase is a very accurate measure of range change with errors on the order of millimeters, because it is the output of an integrator it also has an associated integer ambiguity error. Integer ambiguity is the unknown number of whole cycles of carrier signals between the satellite and antenna. In many applications, such as for in-flight passenger aircraft, quick and accurate attitude determination is critical for safe operation. In order to utilize carrier phase to get the best heading and attitude determinations for such fast moving vehicles, it is necessary to resolve the integer ambiguity quickly and accurately. While existing integer estimation algorithms, such as the LAMBDA (Least-squares AMBiguity Decorrelation Adjustment) algorithm, may provide ambiguity resolutions sufficient for use in precision farming and mining applications, they do not themselves provide sufficiently reliable high integrity solutions in all conditions such that they can be used for flight certified systems aboard aircraft.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for improved systems and methods for vehicle attitude determination.